JP2008085469A - Conductive adhesive and piezoelectric device using the same - Google Patents

Abstract

An object of the present invention is to provide a conductive adhesive capable of improving conductivity without increasing the manufacturing process of a product to be adhered, and a piezoelectric device using the same.
An electrode part for connection of a piezoelectric vibrating piece is fixed to an electrode part for mounting of a package using a conductive adhesive containing a resin component a containing a conductive filler b. In the piezoelectric device configured as described above, the conductive adhesive 42 is a resin whose curing speed at the interface of the metal material 46 is lower than the curing speed at the interface of the conductive filler 42b, the metal material 46, and the conductive filler 42b. And component 42a.
[Selection] Figure 2

Description

  The present invention relates to a conductive adhesive in which a conductive filler is contained in a resin component, and a piezoelectric device using the same.

Piezoelectric devices are widely used in packages in small information devices such as HDDs (hard disk drives), mobile computers, and IC cards, and mobile communication devices such as mobile phones, car phones, and paging systems. Yes.
FIG. 3 is a schematic longitudinal sectional view of a piezoelectric vibrator 1 which is an example of a conventional piezoelectric device.
In the piezoelectric vibrator 1 of this figure, a piezoelectric vibrating piece 5 is accommodated in a package 2.

That is, an electrode portion 8 for mounting is formed on the inner surface of the package 2, and the electrode portion 8 for mounting has tungsten (8a) or the like as a base and gold (Au) 8b having good conductivity in the surface layer portion. is doing.
On the other hand, the piezoelectric vibrating piece 5 has an electrode part 7 for connection formed so that an excitation electrode (not shown) for exciting a piezoelectric body such as quartz crystal is drawn out to the end.
Then, a conductive adhesive 3 containing a resin component 4 containing silver (Ag) particles 6 as a conductive filler is applied to the surface of the electrode portion 8 for mounting, and on the conductive adhesive 3. The electrode portion 7 for connection of the piezoelectric vibrating piece 5 is placed, and then the piezoelectric adhesive piece 5 is bonded to the package 2 by heating and curing the conductive adhesive 3.

  The electrode portion 7 for connecting the piezoelectric vibrating reed 5 usually has gold having good conductivity on the surface with chromium (Cr) as a base, but since gold is relatively expensive, its thickness It is more economical to be as thin as possible. However, if the gold film is thin, the underlying chromium diffuses, and the frequency characteristics of the piezoelectric vibrating reed 5 may change before and after bonding to the package 2. Therefore, in the connection electrode portion 7 in FIG. 3, a chromium film is further formed on chromium and gold so that the frequency before and after the connection to the package 2 does not change (for example, refer to Patent Document 1). .

Japanese Patent Laid-Open No. 2003-198312

  However, the curing rate of the resin component 4 at the interface of the silver particles 6 of the conductive filler contained in the conductive adhesive 3 is faster than the curing rate of the resin component 4 at the interface of the gold 8b of the mounting electrode portion 8. . Then, when the conductive adhesive 3 is heated, there is a possibility that the resin component 4 at the interface of the silver particles 6 is quickly cured and contracted, and the resin component 4 that is not cured around the interface of the electrode portion 8 for mounting. In particular, when a curing inhibitor (not shown) is included in the conductive adhesive 3 to adjust the curing speed, there is a high risk that the curing inhibitor will enter the interface of the electrode portion 8 for mounting. For this reason, a resin layer 9 containing a curing inhibitor is formed between the mounting electrode portion 8 and the silver particles 6, and the resin component 4 and the curing inhibitor are insulative. Will get worse.

  In the case of the piezoelectric device 1 shown in FIG. 3, since the electrode layer 7 for connecting the piezoelectric vibrating reed 5 has a surface layer made of chromium, such deterioration of conductivity occurs on the piezoelectric vibrating reed 5 side. Although it is difficult, since the electrode has a three-layer structure, the manufacturing process of the piezoelectric device 1 must be increased. Further, when the surface layer portion of the connecting electrode portion 7 is made of gold, the same problem as that on the mounting electrode portion 8 side occurs.

  The present invention is for solving the above-mentioned problems, and provides a conductive adhesive capable of improving the conductivity without increasing the manufacturing process of the product to be adhered, and a piezoelectric device using the same. The purpose is to do.

According to the first aspect, the object includes a conductive filler, a metal material, and a resin component having a slow curing rate at the interface of the metal material compared to the cure rate at the interface of the conductive filler. Achieved with a conductive adhesive.
According to the configuration of the first invention, the conductive adhesive has a metal material in addition to the conductive filler, and the resin component is made of the metal material as compared with the curing rate at the interface of the conductive filler. The curing rate at the interface is slow. Then, since the curing rate of the resin component at the interface of the conductive filler is faster, the resin component around the conductive filler contracts quickly, and the resin component turns around the metal material. For this reason, when such a conductive adhesive is fixed to the electrode portion, the amount of the resin component around the electrode portion can be reduced by at least the amount of the resin component around the metal material. Therefore, it is possible to prevent a resin reservoir from being formed between the conductive filler and the electrode part, and to improve the conductivity between the conductive adhesive and the electrode part.
In addition, the conductivity can be improved without increasing the layer structure of the electrode portion of the product to be adhered.
Thus, it is possible to provide a conductive adhesive capable of improving conductivity without increasing the manufacturing process of the product to be adhered.

  According to a second aspect of the present invention, there is provided a piezoelectric device in which an electrode part for connecting a piezoelectric vibrating piece is fixed to an electrode part for mounting a package using a conductive adhesive, The conductive adhesive has a slower curing rate at the interface of the connecting or mounting electrode portion than the curing rate at the interface of the conductive filler, the metal material, and the conductive filler, and the conductive adhesive. And a resin component having a slow curing rate at the interface of the metal material compared to the curing rate at the interface of the conductive filler.

According to the structure of 2nd invention, compared with the hardening rate in the interface of an electroconductive filler about the resin component, the hardening rate in the interface of the electrode part for a connection or a mount is slow. Then, the resin component at the interface of the conductive filler contracts quickly, the resin component wraps around the surface of the electrode part, and a resin reservoir is formed between the conductive filler and the electrode part, resulting in poor conductivity. There is a risk of inviting. However, the conductive adhesive is mixed with a metal material in which the curing rate of the resin component at the interface is slower than the curing rate of the resin component at the interface of the conductive filler. For this reason, the resin also rotates around the metal material, and the amount of the resin component that flows around the surface of the electrode portion can be reduced accordingly. Therefore, it is possible to prevent a resin reservoir from being formed between the conductive filler and the electrode part, and to improve the conductivity between the conductive adhesive and the electrode part.
In addition, the conductivity can be improved without increasing the layer structure of the electrode portion of the piezoelectric device.
Thus, it is possible to provide a piezoelectric device using a conductive adhesive capable of improving the conductivity without increasing the manufacturing process of the product to be adhered.

According to a third invention, in the configuration of the second invention, the metal material includes the same component as the electrode part for connection or the mount.
According to the configuration of the third invention, since the metal material includes the same component as the electrode portion for connection or mount, the curing rate of the resin component at the interface is the same as that of the electrode portion for connection and / or mount. It becomes substantially the same as the curing rate of the resin component at the interface. Therefore, the time when the resin component turns around the metal material and the time when the resin component turns around the electrode portion are substantially the same, and the risk that the resin component turns around and the resin pool is reduced can be reduced.

According to a fourth invention, in the configuration of the second or third invention, the conductive filler is formed of silver or an alloy containing silver, and the metal material is formed of gold or an alloy containing gold. And
According to the configuration of the fourth invention, the conductive filler is made of silver or an alloy containing silver, and the metal material is made of gold or an alloy containing gold. Then, since the curing rate of the resin component at the gold interface is slower than the curing rate of the resin component at the silver interface, the same effects as the second invention are exhibited.

A fifth invention is characterized in that, in the structure of the fourth invention, the resin component is of a silicone type.
According to the configuration of the fifth invention, the resin component is a silicone system. Accordingly, the silicone-based resin is more flexible than other resins such as an epoxy-based resin, so that vibration transmitted between the piezoelectric vibrating piece and the package is absorbed, and so-called vibration leakage is prevented. Can do.

According to a sixth invention, in the configuration of the fifth invention, the metal material is 3% by weight to 10% by weight with respect to the resin component.
In this regard, if the amount of silver or gold in the conductive adhesive is increased too much, the conductive adhesive becomes too hard, and the resin component is made silicone to prevent vibration leakage and the significance is lost. For this reason, it should be kept at least 85% by weight, preferably 78% by weight or less. On the other hand, a conductive filler made of silver is intended to be conductive in the conductive adhesive, and unless this content is 68% by weight or more, the conductive property is deteriorated. For this reason, if the metal material formed from gold exceeds about 10% by weight, the amount of silver or gold in the conductive adhesive increases so that a problem of vibration leakage occurs, or the amount of silver decreases. This may cause deterioration of continuity or cause any problems. The effect of the second invention can be effectively exhibited only when the metal material formed of gold is 3% by weight or more based on the resin component.
Therefore, by setting the metal material formed of gold to 3 to 10% by weight with respect to the resin component, vibration leakage can be effectively prevented and deterioration of conductivity can be prevented.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the accompanying drawings.
1 and 2 show a piezoelectric device 10 according to an embodiment of the present invention. FIG. 1 is a schematic plan view of the piezoelectric device 10, and FIG. 2 is a schematic cross-sectional view taken along line AA of FIG. In addition, the figure enclosed with the dashed-dotted line of FIG. 2 is the elements on larger scale which expanded the electroconductive adhesive agent vicinity of FIG.
In these drawings, the piezoelectric device 10 shows an example in which a piezoelectric vibrator is configured, and the piezoelectric device 10 houses a piezoelectric vibrating piece 20 in a package 30.

The package 30 is formed by, for example, laminating a plurality of substrates formed by molding an aluminum oxide ceramic green sheet as an insulating material, and then sintering. That is, as shown in FIG. 2, in this embodiment, the package 30 is formed by laminating a first substrate 30a and a second substrate 30b from below.
The second substrate 30b is formed with a predetermined hole on the inner side thereof, so that when the second substrate 30b is stacked on the first substrate 30a, an inner space S1 for accommodating the piezoelectric vibrating piece 20 is formed on the inner side of the package 30. Has been. The internal space S1 is sealed by bonding a lid 39 to the upper end surface of the second substrate 30b, that is, the end surface on the opening side of the package 30, using a brazing material 43.

  In the view exposed in the internal space S1 of the first substrate 30a, in the vicinity of the left end portion, for example, for mounting formed by plating nickel (Ni) 40b and gold (Au) 40c on a tungsten metallized 40a as a base Electrode portions 40, 40 are provided. The mounting electrode portions 40 and 40 are electrically connected to the mounting terminals 32 and 32 to supply driving voltages with different polarities so as not to short-circuit as shown in FIG. They are formed at a predetermined interval.

Conductive adhesives 42 and 42 are applied on the mounting electrode portions 40 and 40 by a dispenser or the like. The conductive adhesives 42, 42 are composed of a conductive filler 42 b that exhibits a conduction function and a component such as a resin that exhibits a bonding force (hereinafter referred to as “resin component”, as shown in a diagram surrounded by a one-dot chain line in FIG. 2. 42a).
As the resin component 42a, an epoxy resin or a silicone resin can be used, but in this embodiment, in order to prevent vibration from being transmitted between the piezoelectric vibrating piece 20 and the package 30, a flexible silicone resin is used. These resins are used. The resin component 42a contains a solvent for adjusting viscosity and improving workability in addition to the silicone-based resin. Here, the resin component and the solvent are referred to as a resin component.
As the conductive filler 42b, a powder obtained by making silver particles or copper powder with a silver-plated surface into flakes, spheres, or needles can be used. In this embodiment, general silver particles are used.

  Then, a mounting electrode portion 26 to be described later of the piezoelectric vibrating piece 20 is placed on the conductive adhesives 42 and 42, and the conductive adhesives 42 and 42 are cured by heating at a temperature of 180 ° C. for 1 hour. By doing so, the piezoelectric vibrating piece 20 is fixed to the mounting electrode portions 40, 40.

The piezoelectric vibrating piece 20 is formed of, for example, quartz, and a piezoelectric material such as lithium tantalate or lithium niobate can be used in addition to quartz.
In the case of the present embodiment, the piezoelectric vibrating piece 20 is formed in a small size, and in order to obtain necessary performance, a base portion 21 fixed to the package 30 side, and the base portion 21 is bifurcated toward the right in the drawing. A so-called tuning-fork type piezoelectric vibrating piece having a pair of vibrating arms 22 and 23 extending separately in parallel is used. The piezoelectric vibrating piece 20 is not limited to such a tuning fork type, and various piezoelectric vibrating pieces such as a so-called AT-cut vibrating piece obtained by cutting a piezoelectric material into a rectangular shape can be used.

  Each of the vibrating arms 22 and 23 has long grooves 25 and 25 extending in the length direction. As shown in FIG. 2, each long groove 25, 25 is provided on the front and back surfaces (upper and lower surfaces in FIG. 2) of each vibrating arm 22, 23 and has a substantially H-shaped cross section in the width direction. The excitation electrodes (not shown) provided in the long grooves 25 and the excitation electrodes (not shown) provided on the side surfaces of the vibrating arms 22 and 23 are routed so as to have different polarities. The electric fields in the vibrating arms 22 and 23 are efficiently generated, and the CI value (crystal impedance value) of the piezoelectric vibrating piece 20 is kept low.

Connection portions 26 and 26 having different polarities are formed on portions of the base 51 that support the pair of vibrating arms 22 and 23, in contact with the conductive adhesives 42 and 42.
The connection electrode portions 26 and 26 are electrodes for transmitting a drive voltage to each of the vibrating arms 22 and 23. In the case of this embodiment, as shown in FIG. 1 and FIG. And it is formed in the both ends of the width direction so that it may not short-circuit.
Further, the connecting electrode portions 26 and 26 are formed integrally with excitation electrodes (not shown) provided on the vibrating arms 22 and 23 so as to have different polarities.

These connecting electrode portions 26 and 26 and excitation electrodes (not shown) are formed, for example, by sputtering a base layer of chromium (Cr) 26a and a gold (Au) 26b as a surface layer portion thereon. It is a membrane.
Then, the connecting electrode portions 26 and 26 are placed on the conductive adhesives 42 and 42 described above, and the connecting electrode portions 26 and 26 and the mounting electrode portions 40 and 40 are joined. The piezoelectric vibrating piece 20 is electrically and mechanically connected to the package 30.

Here, at least the surface of the conductive filler 42b in the conductive adhesive 42 is formed of silver (Ag), and the surface portion of the connecting electrode portion 26 and the mounting electrode portion 40 is gold (Au ). Then, when the conductive adhesive 42 is heated, the curing rate of the deposition component such as resin at the interface of the conductive filler 42b is determined by the deposition component such as resin at the interface of the electrode portions 26 and 40 for connection and mounting. It becomes faster than the curing rate. For this reason, the deposition component such as the resin at the interface of the conductive filler 42b contracts quickly, and the resin or the like tries to rotate around the interface of the electrode portions 26 and 40.
However, in the conductive adhesive 42, the curing rate of the resin component (adhesion component) 42a at the interface is slower than the curing rate of the resin component (adhesion component) 42a at the interface of the conductive filler 42b. The metal material 46 is mixed. In other words, for the resin component 42a, the curing rate at the interface of the metal material 46 is slower than the curing rate at the interface of the conductive filler 42b.
For this reason, when the conductive adhesive 42 is heated, the resin component 42a tends to turn around the interface of the metal material 46, and the amount of the resin component 42a trying to turn around the interface of the electrode portions 26 and 40 can be reduced.

In the case of the present embodiment, the metal material 46 is a component in which the curing rate of the resin component 42a at the interface is the same as the curing rate of the resin component 42a at the interface of the connecting electrode part 26 and the mounting electrode part 40. Contains. Specifically, the metal material 46 is made of gold (Au), which is the same material as the surface layer portions of the electrode portions 26 and 40, and the gold is made into a fine particle shape or flake shape between the plurality of conductive fillers 42b. Is mixed.
For this reason, the time when the resin component 42a is about to turn around the metal material 46 and the time when the resin component 42a is about to turn around the electrode portions 26 and 40 can be made substantially the same, so that the resin component 42a can be scattered evenly.

Note that gold (Au), which is the metal material 46, is a material for reducing the amount of the resin component that attempts to travel to the interfaces of the electrode portions 26, 27, and 40, but is in contact with the conductive filler 42b and connected. The electrode portions 26 and 27 for mounting and the electrode portions 40 and 40 for mounting may be helped.
However, if the conductive filler 42b is made of gold, the gold is likely to aggregate and harden, so that it becomes clogged with the nozzle, making it difficult to apply a fine amount to the mounting electrode portion 40. Therefore, it is preferable that the means for achieving conduction is silver particles and gold is added.

Specifically, the gold fine particles as the metal material 46 are made 3 wt% to 10 wt% with respect to the silicone-based resin component 42 a to effectively prevent vibration leakage and prevent deterioration of conductivity. is doing.
That is, if the amount of the silver particles that are the conductive filler 42b and the gold particles that are the metal material 46 are excessively large relative to the resin component 42a, the conductive adhesive 42 becomes too hard and the resin component 42a. The significance of preventing vibration leakage by using a silicone system is lost. For this reason, it is necessary that the conductive filler 42b and the metal material 46 do not exceed at least 85% by weight. In the case of the present embodiment, the vibration leakage is suppressed to 78% by weight or less with respect to the resin component 42a. It works effectively. On the other hand, if the silver particles as the conductive filler 42b are not contained in the resin component 42a by 68% by weight or more, the conductivity is deteriorated.
For this reason, when the metal material 46 exceeds approximately 10% by weight while preventing deterioration of conductivity, the amount of the conductive filler 42b and the metal material 46 may exceed 78% by weight, which may cause a problem of vibration leakage. To do. Alternatively, if the metal material 46 exceeds approximately 10% by weight while preventing the problem of vibration leakage, the amount of the conductive filler 42b may be reduced and the conductivity may be deteriorated.
Therefore, the gold particles as the metal material 46 are preferably 10% by weight with respect to the silicone-based resin component 42a.
Further, by making the gold particles as the metal material 46 3% by weight or more with respect to the resin component 42a, it is possible to effectively reduce the amount of the resin that tries to reach the interface between the electrode portions 26 and 40 for the first time. it can.

The embodiment of the present invention is configured as described above, and the conductive adhesive 42 has a slower curing rate of the resin component 42a at the interface than the curing rate of the resin component 42a at the interface of the conductive filler 42b. A metal material 46 is mixed. For this reason, when the conductive adhesive 42 is heated, the resin also moves around the metal material 46, and the amount of the resin that flows around the surfaces of the electrode portions 26 and 40 can be reduced accordingly. Therefore, it is possible to prevent a resin reservoir from being formed between the conductive filler 42 b and the electrode portions 26 and 40, and to improve the conductivity between the conductive adhesive 40 and the electrode portions 26 and 40.
Further, the conductivity can be improved without increasing the layer structure of the electrode portions 26 and 40 of the piezoelectric device 10.

  The present invention is not limited to the above-described embodiment. Each configuration of each embodiment may be combined with each other as appropriate, or may be omitted and combined with other configurations not shown.

1 is a schematic plan view of a piezoelectric device showing an embodiment of the present invention. The AA line schematic sectional drawing of FIG. FIG. 6 is a schematic longitudinal sectional view of a piezoelectric vibrator which is an example of a conventional piezoelectric device.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Piezoelectric device, 20 ... Piezoelectric vibration piece, 26 ... Connection electrode part, 30 ... Package, 40 ... Mount electrode part, 42 ... Conductive adhesive agent, 42a ... resin component, 42b ... conductive filler, 46 ... metal material

Claims (6)

A conductive filler;
Metal material,
Compared to the curing rate at the interface of the conductive filler, a resin component having a slow curing rate at the interface of the metal material,
A conductive adhesive characterized by comprising: A piezoelectric device in which an electrode portion for connecting a piezoelectric vibrating piece is fixed to an electrode portion for mounting a package using a conductive adhesive,
The conductive adhesive is
The conductive filler;
Metal material,
The curing rate at the interface of the connecting or mounting electrode portion is slower than the curing rate at the interface of the conductive filler, and at the interface of the metal material compared with the curing rate at the interface of the conductive filler. A resin component having a slow curing rate;
A piezoelectric device comprising:   The piezoelectric device according to claim 2, wherein the metal material includes the same component as the electrode part for connection or the mount.   4. The piezoelectric device according to claim 2, wherein the conductive filler is made of silver or an alloy containing silver, and the metal material is made of gold or an alloy containing gold.   The piezoelectric device according to claim 4, wherein the resin component is a silicone system.   The piezoelectric device according to claim 5, wherein the metal material is 3 wt% to 10 wt% with respect to the resin component.

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